This invention is related to a cleaning device for heat exchanger cleaning and particularly to one for large scale heat exchangers for the reduction of soot and/or slag encrustations forming on heat surfaces within the heat exchanger.
During the combustion process of fossil fuels, the internal heat exchange surfaces of boilers become encrusted with slag and soot. In order to enhance the thermal and combustion efficiency of such boilers, it is periodically necessary to reduce the amount of encrustations on the heat exchanger surfaces. Numerous techniques for boiler cleaning are in use today. One approach is the use of so called sootblowers which project a stream of cleaning medium such as air, steam, and water, or mixtures of these materials against the boiler surfaces which causes the accumulated encrustations to be removed through mechanical and thermal shock.
Various types of sootblower systems are used. One type of sootblower is positioned permanently in the boiler and is actuated periodically to eject a sootblowing medium. Other types include the so-called long retracting sootblowers in which a lance tube is periodically advanced into and retracted from the heat exchanger and features one or more nozzles at its outer tip from which the cleaning medium is ejected. The retraction feature of these sootblowers enables the lance tube to be removed from the intense heat within the heat exchanger or boiler which would otherwise damage the lance tube. Many of the retracting sootblower types also cause the lance tube to be simultaneously rotated as it is axially extended into and out of the boiler so that the stream of sootblowing medium traces a helical path during the actuation cycle. Sootblowers are normally operated intermittently in accordance with a schedule which comprehends cleaning requirements, sootblower medium consumption, and various other factors.
In cases where steam or a mixture which includes steam is used as the cleaning medium and the sootblower is actuated intermittently, there is a tendency for the steam which remains in the sootblower associated plumbing to condense between actuation cycles. At the beginning of the next actuation cycle when the cleaning medium is again forced into the lance tube to be ejected from the cleaning nozzles, the condensate is initially expelled in the form of liquid slug. Some condensate will also be formed as the steam initially contacts the relatively cool sootblower internal surfaces. In some conditions, when such a slug of condensate strikes the heat exchange surfaces being cleaned, undesirable boiler tube erosion occurs due to an excessive level of thermal and mechanical shock. Such degradation of the heat exchange surfaces of a boiler can produce catastrophic failures and a significant financial loss for the boiler operator.
This invention is related to a sootblower system incorporating a condensate separating system within the lance tube which causes condensate forming between and during operating cycles to be ejected from the lance tube away from the heat exchange surfaces being cleaned and harmlessly into the interior of the boiler where it is vaporized. The sootblower cleaning nozzles which are aimed at the heat exchange surfaces to be cleaned spray a steam or steam/air mixture relatively free of condensate. Accordingly, this invention is capable of substantially minimizing the erosive effect of the initial output of a slug of condensate against heat exchange surfaces in a boiler. Moreover, the condensate separating effect provided by this invention allows the use of saturated steam or a steam/water mixture for the purposes of cooling the lance tube, while avoiding the degree of heat exchanger erosion which would occur if all the liquid water were sprayed against the heat exchanger surfaces.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.